Dorsam R T, Tuluc M, Kunapuli S P
Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
J Thromb Haemost. 2004 May;2(5):804-12. doi: 10.1111/j.1538-7836.2004.00692.x.
The activated platelet surface serves as an integral part of the prothrombinase complex upon activation by potent platelet agonists such as thrombin and collagen. We determined the receptor specificity through which thrombin was enhancing collagen-induced thrombin generation. Whereas SFLLRN or AYPGKF alone produced minimal thrombin generation or phosphatidylserine exposure through protease activated receptor (PAR) stimulation, they caused a leftward shift in the collagen-induced thrombin generation dose-response curve. Although SFLLRN or AYPGKF potentiated collagen-induced thrombin generation, neither of them potentiated to the same extent as thrombin. However, SFLLRN and AYPGKF together potentiated collagen-induced thrombin generation to the same extent as thrombin. We conclude that thrombin mediates its procoagulant activity through activation of both PAR1 and PAR4 receptors. Similarly, neither PAR1 nor PAR4 stimulation alone mimicked the annexin V-binding response caused by thrombin stimulation. The combination of PAR activating peptides caused minimal increases in annexin V binding, but caused significant thrombin generation, suggesting that events other than phosphatidylserine exposure may play a role in platelet prothrombinase complex formation. We also investigated the ability of ADP to potentiate agonist-induced thrombin generation. Whereas P2Y(1) antagonism did not affect collagen or thrombin-induced thrombin generation, P2Y(12) antagonism did decrease both collagen- and thrombin-induced thrombin generation, suggesting that ADP potentiates thrombin generation primarily through the P2Y(12) receptor. Collectively, these results suggest that stimulation of both the PAR1 and PAR4 receptors are necessary for thrombin-induced procoagulant activity, and that the P2Y(12) receptor, but not the P2Y(1) receptor, is responsible for the potentiation of agonist-induced platelet procoagulant activity.
在被凝血酶和胶原蛋白等强效血小板激动剂激活后，活化的血小板表面成为凝血酶原酶复合物不可或缺的一部分。我们确定了凝血酶增强胶原蛋白诱导的凝血酶生成所通过的受体特异性。单独的SFLLRN或AYPGKF通过蛋白酶激活受体（PAR）刺激产生的凝血酶生成或磷脂酰丝氨酸暴露极少，但它们使胶原蛋白诱导的凝血酶生成剂量反应曲线向左移动。尽管SFLLRN或AYPGKF增强了胶原蛋白诱导的凝血酶生成，但它们都没有达到与凝血酶相同的增强程度。然而，SFLLRN和AYPGKF共同作用时，增强胶原蛋白诱导的凝血酶生成的程度与凝血酶相同。我们得出结论，凝血酶通过激活PAR1和PAR4受体来介导其促凝血活性。同样，单独刺激PAR1或PAR4都不能模拟凝血酶刺激引起的膜联蛋白V结合反应。PAR激活肽的组合导致膜联蛋白V结合的增加极少，但却引起显著的凝血酶生成，这表明除磷脂酰丝氨酸暴露之外的其他事件可能在血小板凝血酶原酶复合物形成中起作用。我们还研究了ADP增强激动剂诱导的凝血酶生成的能力。P2Y(1)拮抗剂不影响胶原蛋白或凝血酶诱导的凝血酶生成，而P2Y(12)拮抗剂确实降低了胶原蛋白和凝血酶诱导的凝血酶生成，这表明ADP主要通过P2Y(12)受体增强凝血酶生成。总体而言，这些结果表明，PAR1和PAR4受体的刺激对于凝血酶诱导的促凝血活性是必需的，并且P2Y(12)受体而非P2Y(1)受体负责增强激动剂诱导的血小板促凝血活性。
